The present invention relates to a process for converting methane gases to high hydrocarbons, a catalyst for use in such processes and a method for preparing such a catalyst.
Methods for conversion of methane to high hydrocarbons are typically carried out using metal-based catalysts. Among the known conversion processes, catalysts based on manganese, magnesium and lead using alkali metal promoters have given good results in synthesis of methane to obtain ethane/ethylene type products. Among these catalysts used in such processes, catalysts based upon oxides of manganese have been extensively studied and described.
U.S. Pat. No. 4,499,322 to Jones et al. discloses a process of methane conversion using an oxidative synthesizing agent containing a promoting amount of alkali metal and/or compounds thereof.
U.S. Pat. No. 4,547,608 discloses the use of a support material for a catalyst which comprises alkaline earth metal oxides and silicon oxides, alumina and mixtures thereof.
Published European Patent Application No. 0316075-A1 discloses a process for conversion of methane to higher hydrocarbons using a catalyst comprising manganese oxides which incorporate at least one of the elements tin, titanium, tungsten, tantalum, silicon, germanium, lead, phosphorus, arsenic, antimony, boron, gallium, indium, a lanthanide or an actinide. The method for preparation of this catalyst is disclosed as comprising the steps of calcining the manganese dioxide at 1000.degree. C. for 16 hours to obtain Mn.sub.3 O.sub.4, which is impregnated with a solution of sodium chloride and finally diluted with fines of silica.
Published European Patent Application No. 0365181-A1 discloses a process for preparation of a cogel catalyst for use in conversion of methane to higher hydrocarbons. The disclosed process involves the mixing of an aqueous solution of a soluble salt of an alkali or alkaline earth metal with a solution of a soluble compound of a metal thermally decomposable to a metal oxide. A solution in a hydroxylic solvent of a hydrolyzable silane is then added to this mixture, and this mixture is then maintained under such conditions that the mixture forms a cogel, while avoiding the formation of precipitates or particles. This cogel is then dried and calcined to obtain the desired catalyst.
While the above-described catalysts obtain satisfactory initial conversion rates of methane to higher hydrocarbons, this initial activity decreases rapidly during reaction time.
Accordingly, it is the principal object of the present invention to disclose a catalyst which possesses high conversion rates which do not rapidly decrease during reaction time, and a method for preparation of such a catalyst.
It is a further object of the present invention to provide a process for the conversion of methane to higher hydrocarbons which utilizes a catalyst prepared according to the present invention, to yield enhanced results in the conversion process.
Other aspects, objectives and advantages of the present invention will be apparent to those skilled in the art after a consideration of the accompanying detailed description of the invention and figures which are referred to therein.